Systems and methods for estimating a volume of activation using a compressed database of threshold values

ABSTRACT

A system for estimating a volume of activation around an implanted electrical stimulation lead for a set of stimulation parameters includes a display; and a processor coupled to the display and configured to: receive a set of stimulation parameters including a stimulation amplitude and a selection of one of more electrodes of the implanted electrical stimulation lead for delivery of the stimulation amplitude; determine an estimate of the volume of activation based on the set of stimulation parameters using the stimulation amplitude and a database including a plurality of planar distributions of stimulation threshold values and a map relating the planar distributions to spatial locations based on the one or more electrodes of the implanted electrical stimulation lead selected for delivery of the stimulation amplitude; and output on the display a graphical representation of the estimate of the volume of activation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Patent Application Ser. No. 62/480,942, filed Apr. 3, 2017,which is incorporated herein by reference.

FIELD

The invention is directed to the field of electrical stimulationsystems. The present invention is also directed to systems and methodsfor estimating a volume of activation, as well as methods of making andusing systems.

BACKGROUND

Electrical stimulation can be useful for treating a variety ofconditions. Deep brain stimulation can be useful for treating, forexample, Parkinson's disease, dystonia, essential tremor, chronic pain,Huntington's disease, levodopa-induced dyskinesias and rigidity,bradykinesia, epilepsy and seizures, eating disorders, and mooddisorders. Typically, a lead with a stimulating electrode at or near atip of the lead provides the stimulation to target neurons in the brain.Magnetic resonance imaging (“MRI”) or computerized tomography (“CT”)scans can provide a starting point for determining where the stimulatingelectrode should be positioned to provide the desired stimulus to thetarget neurons.

After the lead is implanted into a patient's brain, electrical stimuluscurrent can be delivered through selected electrodes on the lead tostimulate target neurons in the brain. The electrodes can be formed intorings or segments disposed on a distal portion of the lead. The stimuluscurrent projects from the electrodes. Using segmented electrodes canprovide directionality to the stimulus current and permit a clinician tosteer the current to a desired direction and stimulation field.

BRIEF SUMMARY

One embodiment is a system for estimating a volume of activation aroundan implanted electrical stimulation lead for a set of stimulationparameters. The system includes a display; and a processor coupled tothe display and configured to: receive a set of stimulation parametersincluding a stimulation amplitude and a selection of one of moreelectrodes of the implanted electrical stimulation lead for delivery ofthe stimulation amplitude; determine an estimate of the volume ofactivation based on the set of stimulation parameters using thestimulation amplitude and a database including a plurality of planardistributions of stimulation threshold values and a map relating theplanar distributions to spatial locations based on the one or moreelectrodes of the implanted electrical stimulation lead selected fordelivery of the stimulation amplitude; and output, on the display, agraphical representation of the estimate of the volume of activation.

Another embodiment is a non-transitory computer-readable medium havingcomputer executable instructions stored thereon that, when executed byat least one processor, cause the at least one processor to perform theinstructions, the instructions including: receiving a set of stimulationparameters including a stimulation amplitude and a selection of one ofmore electrodes of the implanted electrical stimulation lead fordelivery of the stimulation amplitude; determining an estimate of thevolume of activation based on the set of stimulation parameters usingthe stimulation amplitude and a database including a plurality of planardistributions of stimulation threshold values and a map relating theplanar distributions to spatial locations based on the one or moreelectrodes of the implanted electrical stimulation lead selected fordelivery of the stimulation amplitude; and outputting, on the display, agraphical representation of the estimate of the volume of activation.

In at least some embodiments of the system or the non-transitorycomputer-readable medium, the database consists of the plurality ofplanar distributions, wherein each of the planar distributions isunique. In at least some embodiments, the database is a losslesscompressed database. In at least some embodiments, the database is alossy compressed database.

In at least some embodiments of the system or the non-transitorycomputer-readable medium, the map includes a plurality of entries,wherein each entry is indexed to a selection of the one or moreelectrodes and an angular location around the implanted electricalstimulation lead. In at least some embodiments, the selection of the oneor more electrodes is characterized by at least one fractionalizationparameter. In at least some embodiments, the at least onefractionalization parameter includes at least one of an axial positionparameter, an angular direction parameter, or an angular spreadparameter. In at least some embodiments, the selection of the one ormore electrodes is characterized by an axial position parameter, anangular direction parameter, and an angular spread parameter. In atleast some embodiments, at least two of the entries of the map point toa same planar distribution. In at least some embodiments of the systemor the non-transitory computer-readable medium, the at least two of theentries include a first entry corresponding to a selection of a firstone of the electrodes and a first angular location and a second entrycorresponding to a selection of a second one of the electrodes and asecond angular location, wherein the first angular location and thesecond angular location differ by a first angle, wherein a location ofthe first one of the electrodes differs from a location of the secondone of the electrodes by the first angle.

Yet another embodiment is a system for estimating a volume of activationaround an implanted electrical stimulation lead for a set of stimulationparameters. The system includes a processor configured to: receive aplurality of planar distributions of stimulation threshold values foreach of a plurality of sets of stimulation parameters, each of the setsof stimulation parameters includes a stimulation amplitude and aselection of one of more electrodes of the implanted electricalstimulation lead for delivery of the stimulation amplitude; compress theplurality of planar distributions of stimulation threshold values into acompressed database including a plurality of unique planar distributionsof stimulation threshold values; and generate a map relating the uniqueplanar distributions of stimulation threshold values to the planardistributions of stimulation threshold values for the multiple sets ofstimulation parameters.

In at least some embodiments, the compressing includes compress theplurality of planar distributions of stimulation threshold values into acompressed database using a lossless compression technique. In at leastsome embodiments, the compressing includes compress the plurality ofplanar distributions of stimulation threshold values into a compresseddatabase using a lossy compression technique.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention aredescribed with reference to the following drawings. In the drawings,like reference numerals refer to like parts throughout the variousfigures unless otherwise specified.

For a better understanding of the present invention, reference will bemade to the following Detailed Description, which is to be read inassociation with the accompanying drawings, wherein:

FIG. 1 is a schematic side view of one embodiment of a device for brainstimulation, according to the invention;

FIG. 2 is a schematic diagram of radial current steering along variouselectrode levels along the length of a lead, according to the invention;

FIG. 3A is a perspective view of an embodiment of a portion of a leadhaving a plurality of segmented electrodes, according to the invention;

FIG. 3B is a perspective view of a second embodiment of a portion of alead having a plurality of segmented electrodes, according to theinvention;

FIG. 3C is a perspective view of a third embodiment of a portion of alead having a plurality of segmented electrodes, according to theinvention;

FIG. 3D is a perspective view of a fourth embodiment of a portion of alead having a plurality of segmented electrodes, according to theinvention;

FIG. 3E is a perspective view of a fifth embodiment of a portion of alead having a plurality of segmented electrodes, according to theinvention;

FIG. 3F is a perspective view of a sixth embodiment of a portion of alead having a plurality of segmented electrodes, according to theinvention;

FIG. 3G is a perspective view of a seventh embodiment of a portion of alead having a plurality of segmented electrodes, according to theinvention;

FIG. 3H is a perspective view of an eighth embodiment of a portion of alead having a plurality of segmented electrodes, according to theinvention;

FIG. 4A is a graphical illustration of one embodiment of a set of planesrelative to a lead for facilitating estimating a volume of activation,according to the invention;

FIG. 4B illustrates examples of planar distributions of stimulationthreshold values, according to the invention;

FIG. 5 is a schematic illustration of one embodiment of a system forpracticing the invention;

FIG. 6 is a perspective view of a portion of a lead having a pluralityof segmented electrodes for use as an example, according to theinvention;

FIG. 7 is a schematic representation of relationship between a full setof I_(th) tables and a compressed set of unique I_(th) tables related bya map, according to the invention;

FIG. 8 is a schematic representation of relationship between a full setof I_(th) tables and a compressed set of unique, approximate I_(th)tables related by a map, according to the invention;

FIG. 9 is a schematic flowchart of a one embodiment of a method ofestimating a volume of activation, according to the invention;

FIG. 10 is a schematic flowchart of one embodiment of a method ofcompressing a set of planar distributions of stimulation thresholdvalues into a compressed database, according to the invention; and

FIG. 11 is a schematic flowchart of one embodiment of a method ofdecompressing a compressed database, according to the invention.

DETAILED DESCRIPTION

The invention is directed to the field of electrical stimulationsystems. The present invention is also directed to systems and methodsfor estimating a volume of activation, as well as methods of making andusing systems.

A lead for electrical stimulation can include one or more stimulationelectrodes. In at least some embodiments, one or more of the stimulationelectrodes are provided in the form of segmented electrodes that extendonly partially around the circumference of the lead. These segmentedelectrodes can be provided in sets of electrodes, with each set havingelectrodes radially distributed about the lead at a particular axialposition. For illustrative purposes, the leads are described hereinrelative to use for deep brain stimulation, but it will be understoodthat any of the leads can be used for applications other than deep brainstimulation, including spinal cord stimulation, peripheral nervestimulation, dorsal root ganglia stimulation, vagal nerve stimulation,basoreceptor stimulation, or stimulation of other nerves, organs, ortissues.

Suitable implantable electrical stimulation systems include, but are notlimited to, at least one lead with one or more electrodes disposed on adistal end of the lead and one or more terminals disposed on one or moreproximal ends of the lead. Leads include, for example, percutaneousleads. Examples of electrical stimulation systems with leads are foundin, for example, U.S. Pat. Nos. 6,181,969; 6,516,227; 6,609,029;6,609,032; 6,741,892; 7,244,150; 7,450,997; 7,672,734;7,761,165;7,783,359; 7,792,590; 7,809,446; 7,949,395; 7,974,706; 8,175,710;8,224,450; 8,271,094; 8,295,944; 8,364,278; 8,391,985; and 8,688,235;and U.S. Patent Applications Publication Nos. 2007/0150036;2009/0187222; 2009/0276021; 2010/0076535; 2010/0268298; 2011/0005069;2011/0004267; 2011/0078900; 2011/0130817; 2011/0130818; 2011/0238129;2011/0313500; 2012/0016378; 2012/0046710; 2012/0071949; 2012/0165911;2012/0197375; 2012/0203316; 2012/0203320; 2012/0203321; 2012/0316615;2013/0105071; and 2013/0197602, all of which are incorporated byreference.

In at least some embodiments, a practitioner may determine the positionof the target neurons using recording electrode(s) and then position thestimulation electrode(s) accordingly. In some embodiments, the sameelectrodes can be used for both recording and stimulation. In someembodiments, separate leads can be used; one with recording electrodeswhich identify target neurons, and a second lead with stimulationelectrodes that replaces the first after target neuron identification.In some embodiments, the same lead can include both recording electrodesand stimulation electrodes or electrodes can be used for both recordingand stimulation.

FIG. 1 illustrates one embodiment of a device 100 for electricalstimulation (for example, brain or spinal cord stimulation). The deviceincludes a lead 110, a plurality of electrodes 125 disposed at leastpartially about a circumference of the lead 110, a plurality ofterminals 135, a connector 132 for connection of the electrodes to acontrol module, and a stylet 140 for assisting in insertion andpositioning of the lead in the patient's brain. The stylet 140 can bemade of a rigid material. Examples of suitable materials for the styletinclude, but are not limited to, tungsten, stainless steel, and plastic.The stylet 140 may have a handle 150 to assist insertion into the lead110, as well as rotation of the stylet 140 and lead 110. The connector132 fits over a proximal end of the lead 110, preferably after removalof the stylet 140. The connector 132 can be part of a control module orcan be part of an optional lead extension that is coupled to the controlmodule.

The control module (for example, control module 514 of FIG. 5) can be animplantable pulse generator that can be implanted into a patient's body,for example, below the patient's clavicle area. The control module canhave eight stimulation channels which may be independently programmableto control the magnitude of the current stimulus from each channel. Insome cases, the control module can have more or fewer than eightstimulation channels (e.g., 4-, 6-, 16-, 32-, or more stimulationchannels). The control module can have one, two, three, four, or moreconnector ports, for receiving the plurality of terminals 135 at theproximal end of the lead 110. Examples of control modules are describedin the references cited above.

In one example of operation, access to the desired position in the braincan be accomplished by drilling a hole in the patient's skull or craniumwith a cranial drill (commonly referred to as a burr), and coagulatingand incising the dura mater, or brain covering. The lead 110 can beinserted into the cranium and brain tissue with the assistance of thestylet 140. The lead 110 can be guided to the target location within thebrain using, for example, a stereotactic frame and a microdrive motorsystem. In some embodiments, the microdrive motor system can be fully orpartially automatic. The microdrive motor system may be configured toperform one or more the following actions (alone or in combination):insert the lead 110, retract the lead 110, or rotate the lead 110.

In some embodiments, measurement devices coupled to the muscles or othertissues stimulated by the target neurons, or a unit responsive to thepatient or clinician, can be coupled to the control module or microdrivemotor system. The measurement device, user, or clinician can indicate aresponse by the target muscles or other tissues to the stimulation orrecording electrode(s) to further identify the target neurons andfacilitate positioning of the stimulation electrode(s). For example, ifthe target neurons are directed to a muscle experiencing tremors, ameasurement device can be used to observe the muscle and indicatechanges in tremor frequency or amplitude in response to stimulation ofneurons. Alternatively, the patient or clinician can observe the muscleand provide feedback.

The lead 110 for deep brain stimulation can include stimulationelectrodes, recording electrodes, or both. In at least some embodiments,the lead 110 is rotatable so that the stimulation electrodes can bealigned with the target neurons after the neurons have been locatedusing the recording electrodes.

Stimulation electrodes may be disposed on the circumference of the lead110 to stimulate the target neurons. Stimulation electrodes may bering-shaped so that current projects from each electrode equally inevery direction from the position of the electrode along a length of thelead 110. Ring electrodes typically do not enable stimulus current to bedirected from only a limited angular range around of the lead. Segmentedelectrodes, however, can be used to direct stimulation energy to aselected angular range around the lead. When segmented electrodes areused in conjunction with an implantable control module that deliversconstant current stimulus, current steering can be achieved to moreprecisely deliver the stimulus to one or more particular angular rangesaround an axis of the lead.

To achieve current steering, segmented electrodes can be utilized inaddition to, or as an alternative to, ring electrodes. Though thefollowing description discusses stimulation electrodes, it will beunderstood that all configurations of the stimulation electrodesdiscussed may be utilized in arranging recording electrodes as well. Alead that includes segmented electrodes can be referred to as adirectional lead because the segmented electrodes can be used to directstimulation along a particular direction or range of directions.

The lead 100 includes a lead body 110, one or more optional ringelectrodes 120, and a plurality of sets of segmented electrodes 130. Thelead body 110 can be formed of a biocompatible, non-conducting materialsuch as, for example, a polymeric material. Suitable polymeric materialsinclude, but are not limited to, silicone, polyurethane, polyurea,polyurethane-urea, polyethylene, or the like. Once implanted in thebody, the lead 100 may be in contact with body tissue for extendedperiods of time. In at least some embodiments, the lead 100 has across-sectional diameter of no more than 1.5 mm and may be in the rangeof 0.5 to 1.5 mm. In at least some embodiments, the lead 100 has alength of at least 10 cm and the length of the lead 100 may be in therange of 10 to 70 cm.

The electrodes can be made using a metal, alloy, conductive oxide, orany other suitable conductive biocompatible material. Examples ofsuitable materials include, but are not limited to, platinum, platinumiridium alloy, iridium, titanium, tungsten, palladium, palladiumrhodium, or the like. Preferably, the electrodes are made of a materialthat is biocompatible and does not substantially corrode under expectedoperating conditions in the operating environment for the expectedduration of use.

Each of the electrodes can either be used or unused (OFF). When theelectrode is used, the electrode can be used as an anode or cathode andcarry anodic or cathodic current. In some instances, an electrode mightbe an anode for a period of time and a cathode for a period of time.

Stimulation electrodes in the form of ring electrodes 120 can bedisposed on any part of the lead body 110, usually near a distal end ofthe lead 100. In FIG. 1, the lead 100 includes two ring electrodes 120.Any number of ring electrodes 120 can be disposed along the length ofthe lead body 110 including, for example, one, two three, four, five,six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen,fifteen, sixteen or more ring electrodes 120. It will be understood thatany number of ring electrodes can be disposed along the length of thelead body 110. In some embodiments, the ring electrodes 120 aresubstantially cylindrical and wrap around the entire circumference ofthe lead body 110. In some embodiments, the outer diameters of the ringelectrodes 120 are substantially equal to the outer diameter of the leadbody 110. The length of the ring electrodes 120 may vary according tothe desired treatment and the location of the target neurons. In someembodiments the length of the ring electrodes 120 are less than or equalto the diameters of the ring electrodes 120. In other embodiments, thelengths of the ring electrodes 120 are greater than the diameters of thering electrodes 120. The distal-most ring electrode 120 may be a tipelectrode (see, e.g., tip electrode 320 a of FIG. 3E) which covers most,or all, of the distal tip of the lead.

Deep brain stimulation leads may include one or more sets of segmentedelectrodes. Segmented electrodes may provide for superior currentsteering than ring electrodes because target structures in deep brainstimulation are not typically symmetric about the axis of the distalelectrode array. Instead, a target may be located on one side of a planerunning through the axis of the lead. Through the use of a radiallysegmented electrode array, current steering can be performed not onlyalong a length of the lead but also around a circumference of the lead.This provides precise three-dimensional targeting and delivery of thecurrent stimulus to neural target tissue, while potentially avoidingstimulation of other tissue. Examples of leads with segmented electrodesinclude U.S. Patent Applications Publication Nos. 2010/0268298;2011/0005069; 2011/0078900; 2011/0130803; 2011/0130816; 2011/0130817;2011/0130818; 2011/0078900; 2011/0238129; 2011/0313500; 2012/0016378;2012/0046710; 2012/0071949; 2012/0165911; 2012/197375; 2012/0203316;2012/0203320; 2012/0203321; 2013/0197602; 2013/0261684; 2013/0325091;2013/0317587; 2014/0039587; 2014/0353001; 2014/0358209; 2014/0358210;2015/0018915; 2015/0021817; 2015/0045864; 2015/0021817; 2015/0066120;2013/0197424; 2015/0151113; 2014/0358207; and U.S. Pat. No. 8,483,237,all of which are incorporated herein by reference in their entireties.Examples of leads with tip electrodes include at least some of thepreviously cited references, as well as U.S. Patent ApplicationsPublication Nos. 2014/0296953 and 2014/0343647, all of which areincorporated herein by reference in their entireties.

The lead 100 is shown having a plurality of segmented electrodes 130.Any number of segmented electrodes 130 may be disposed on the lead body110 including, for example, one, two three, four, five, six, seven,eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteenor more segmented electrodes 130. It will be understood that any numberof segmented electrodes 130 may be disposed along the length of the leadbody 110. A segmented electrode 130 typically extends only 75%, 67%,60%, 50%, 40%, 33%, 25%, 20%, 17%, 15%, or less around the circumferenceof the lead.

The segmented electrodes 130 may be grouped into sets of segmentedelectrodes, where each set is disposed around a circumference of thelead 100 at a particular longitudinal portion of the lead 100. The lead100 may have any number segmented electrodes 130 in a given set ofsegmented electrodes. The lead 100 may have one, two, three, four, five,six, seven, eight, or more segmented electrodes 130 in a given set. Inat least some embodiments, each set of segmented electrodes 130 of thelead 100 contains the same number of segmented electrodes 130. Thesegmented electrodes 130 disposed on the lead 100 may include adifferent number of electrodes than at least one other set of segmentedelectrodes 130 disposed on the lead 100.

The segmented electrodes 130 may vary in size and shape. In someembodiments, the segmented electrodes 130 are all of the same size,shape, diameter, width or area or any combination thereof. In someembodiments, the segmented electrodes 130 of each circumferential set(or even all segmented electrodes disposed on the lead 100) may beidentical in size and shape.

Each set of segmented electrodes 130 may be disposed around thecircumference of the lead body 110 to form a substantially cylindricalshape around the lead body 110. The spacing between individualelectrodes of a given set of the segmented electrodes may be the same,or different from, the spacing between individual electrodes of anotherset of segmented electrodes on the lead 100. In at least someembodiments, equal spaces, gaps or cutouts are disposed between eachsegmented electrode 130 around the circumference of the lead body 110.In other embodiments, the spaces, gaps or cutouts between the segmentedelectrodes 130 may differ in size or shape. In other embodiments, thespaces, gaps, or cutouts between segmented electrodes 130 may be uniformfor a particular set of the segmented electrodes 130, or for all sets ofthe segmented electrodes 130. The sets of segmented electrodes 130 maybe positioned in irregular or regular intervals along a length the leadbody 110.

Conductor wires that attach to the ring electrodes 120 or segmentedelectrodes 130 extend along the lead body 110. These conductor wires mayextend through the material of the lead 100 or along one or more lumensdefined by the lead 100, or both. The conductor wires couple theelectrodes 120, 130 to the terminals 135.

When the lead 100 includes both ring electrodes 120 and segmentedelectrodes 130, the ring electrodes 120 and the segmented electrodes 130may be arranged in any suitable configuration. For example, when thelead 100 includes two ring electrodes 120 and two sets of segmentedelectrodes 130, the ring electrodes 120 can flank the two sets ofsegmented electrodes 130 (see e.g., FIGS. 1, 3A, and 3E-3H—ringelectrodes 320 and segmented electrode 330). Alternately, the two setsof ring electrodes 120 can be disposed proximal to the two sets ofsegmented electrodes 130 (see e.g., FIG. 3C—ring electrodes 320 andsegmented electrode 330), or the two sets of ring electrodes 120 can bedisposed distal to the two sets of segmented electrodes 130 (see e.g.,FIG. 3D—ring electrodes 320 and segmented electrode 330). One of thering electrodes can be a tip electrode (see, tip electrode 320 a ofFIGS. 3E and 3G). It will be understood that other configurations arepossible as well (e.g., alternating ring and segmented electrodes, orthe like).

By varying the location of the segmented electrodes 130, differentcoverage of the target neurons may be selected. For example, theelectrode arrangement of FIG. 3C may be useful if the physiciananticipates that the neural target will be closer to a distal tip of thelead body 110, while the electrode arrangement of FIG. 3D may be usefulif the physician anticipates that the neural target will be closer to aproximal end of the lead body 110.

Any combination of ring electrodes 120 and segmented electrodes 130 maybe disposed on the lead 100. For example, the lead may include a firstring electrode 120, two sets of segmented electrodes; each set formed offour segmented electrodes 130, and a final ring electrode 120 at the endof the lead. This configuration may simply be referred to as a 1-4-4-1configuration (FIGS. 3A and 3E—ring electrodes 320 and segmentedelectrode 330). It may be useful to refer to the electrodes with thisshorthand notation. Thus, the embodiment of FIG. 3C may be referred toas a 1-1-4-4 configuration, while the embodiment of FIG. 3D may bereferred to as a 4-4-1-1 configuration. The embodiments of FIGS. 3F, 3G,and 3H can be referred to as a 1-3-3-1 configuration. Other electrodeconfigurations include, for example, a 2-2-2-2 configuration, where foursets of segmented electrodes are disposed on the lead, and a 4-4configuration, where two sets of segmented electrodes, each having foursegmented electrodes 130 are disposed on the lead. The 1-3-3-1 electrodeconfiguration of FIGS. 3F, 3G, and 3H has two sets of segmentedelectrodes, each set containing three electrodes disposed around thecircumference of the lead, flanked by two ring electrodes (FIGS. 3F and3H) or a ring electrode and a tip electrode (FIG. 3G). In someembodiments, the lead includes 16 electrodes. Possible configurationsfor a 16-electrode lead include, but are not limited to 4-4-4-4; 8-8;3-3-3-3-3-1 (and all rearrangements of this configuration); and2-2-2-2-2-2-2-2.

FIG. 2 is a schematic diagram to illustrate radial current steeringalong various electrode levels along the length of the lead 200. Whileconventional lead configurations with ring electrodes are only able tosteer current along the length of the lead (the z-axis), the segmentedelectrode configuration is capable of steering current in the x-axis,y-axis as well as the z-axis. Thus, the centroid of stimulation may besteered in any direction in the three-dimensional space surrounding thelead 200. In some embodiments, the radial distance, r, and the angle 0around the circumference of the lead 200 may be dictated by thepercentage of anodic current (recognizing that stimulation predominantlyoccurs near the cathode, although strong anodes may cause stimulation aswell) introduced to each electrode. In at least some embodiments, theconfiguration of anodes and cathodes along the segmented electrodesallows the centroid of stimulation to be shifted to a variety ofdifferent locations along the lead 200.

As can be appreciated from FIG. 2, the stimulation can be shifted ateach level along the length L of the lead 200. The use of multiple setsof segmented electrodes at different levels along the length of the leadallows for three-dimensional current steering. In some embodiments, thesets of segmented electrodes are shifted collectively (i.e., thecentroid of simulation is similar at each level along the length of thelead). In at least some other embodiments, each set of segmentedelectrodes is controlled independently. Each set of segmented electrodesmay contain two, three, four, five, six, seven, eight or more segmentedelectrodes. It will be understood that different stimulation profilesmay be produced by varying the number of segmented electrodes at eachlevel. For example, when each set of segmented electrodes includes onlytwo segmented electrodes, uniformly distributed gaps (inability tostimulate selectively) may be formed in the stimulation profile. In someembodiments, at least three segmented electrodes in a set are utilizedto allow for true 360° selectivity.

Turning to FIGS. 3A-3H, when the lead 300 includes a plurality of setsof segmented electrodes 330, it may be desirable to form the lead 300such that corresponding electrodes of different sets of segmentedelectrodes 330 are radially aligned with one another along the length ofthe lead 300 (see e.g., the segmented electrodes 330 shown in FIGS. 3Aand 3C-3G). Radial alignment between corresponding electrodes ofdifferent sets of segmented electrodes 330 along the length of the lead300 may reduce uncertainty as to the location or orientation betweencorresponding segmented electrodes of different sets of segmentedelectrodes. Accordingly, it may be beneficial to form electrode arrayssuch that corresponding electrodes of different sets of segmentedelectrodes along the length of the lead 300 are radially aligned withone another and do not radially shift in relation to one another duringmanufacturing of the lead 300.

In other embodiments, individual electrodes in the two sets of segmentedelectrodes 330 are staggered (see, FIG. 3H) relative to one anotheralong the length of the lead body 310. In some cases, the staggeredpositioning of corresponding electrodes of different sets of segmentedelectrodes along the length of the lead 300 may be designed for aspecific application.

Segmented electrodes can be used to tailor the stimulation region sothat, instead of stimulating tissue around the circumference of the leadas would be achieved using a ring electrode, the stimulation region canbe directionally targeted. In some instances, it is desirable to targeta parallelepiped (or slab) region 250 that contains the electrodes ofthe lead 200, as illustrated in FIG. 2. One arrangement for directing astimulation field into a parallelepiped region uses segmented electrodesdisposed on opposite sides of a lead.

FIGS. 3A-3H illustrate leads 300 with segmented electrodes 330, optionalring electrodes 320 or tip electrodes 320 a, and a lead body 310. Thesets of segmented electrodes 330 each include either two (FIG. 3B),three (FIGS. 3E-3H), or four (FIGS. 3A, 3C, and 3D) or any other numberof segmented electrodes including, for example, three, five, six, ormore. The sets of segmented electrodes 330 can be aligned with eachother (FIGS. 3A-3G) or staggered (FIG. 3H)

Any other suitable arrangements of segmented electrodes can be used. Asan example, arrangements in which segmented electrodes are arrangedhelically with respect to each other. One embodiment includes a doublehelix.

FIG. 5 illustrates one embodiment of a system for practicing theinvention. The system can include a computer 500 or any other similardevice that includes a processor 502 and a memory 504, a display 506, aninput device 508, and, optionally, the electrical stimulation system512.

The computer 500 can be a laptop computer, desktop computer, tablet,mobile device, smartphone or other devices that can run applications orprograms, or any other suitable device for processing information andfor presenting a user interface. The computer can be, for example, aclinician programmer, patient programmer, or remote programmer for theelectrical stimulation system 512. The computer 500 can be local to theuser or can include components that are non-local to the user includingone or both of the processor 502 or memory 504 (or portions thereof).For example, in some embodiments, the user may operate a terminal thatis connected to a non-local computer. In other embodiments, the memorycan be non-local to the user.

The computer 500 can utilize any suitable processor 502 including one ormore hardware processors that may be local to the user or non-local tothe user or other components of the computer. The processor 502 isconfigured to execute instructions provided to the processor, asdescribed below.

Any suitable memory 504 can be used for the computer 502. The memory 504illustrates a type of computer-readable media, namely computer-readablestorage media. Computer-readable storage media may include, but is notlimited to, nonvolatile, non-transitory, removable, and non-removablemedia implemented in any method or technology for storage ofinformation, such as computer readable instructions, data structures,program modules, or other data. Examples of computer-readable storagemedia include RAM, ROM, EEPROM, flash memory, or other memorytechnology, CD-ROM, digital versatile disks (“DVD”) or other opticalstorage, magnetic cassettes, magnetic tape, magnetic disk storage orother magnetic storage devices, or any other medium which can be used tostore the desired information and which can be accessed by a computer.

Communication methods provide another type of computer readable media;namely communication media. Communication media typically embodiescomputer-readable instructions, data structures, program modules, orother data in a modulated data signal such as a carrier wave, datasignal, or other transport mechanism and include any informationdelivery media. The terms “modulated data signal,” and “carrier-wavesignal” includes a signal that has one or more of its characteristicsset or changed in such a manner as to encode information, instructions,data, and the like, in the signal. By way of example, communicationmedia includes wired media such as twisted pair, coaxial cable, fiberoptics, wave guides, and other wired media and wireless media such asacoustic, RF, infrared, and other wireless media.

The display 506 can be any suitable display device, such as a monitor,screen, display, or the like, and can include a printer. The inputdevice 508 can be, for example, a keyboard, mouse, touch screen, trackball, joystick, voice recognition system, or any combination thereof, orthe like and can be used by the user to interact with a user interfaceor clinical effects map.

The electrical stimulation system 512 can include, for example, acontrol module 514 (for example, an implantable pulse generator) and alead 516 (for example, the lead illustrated in FIG. 1.) The electricalstimulation system 512 may communicate with the computer 500 through awired or wireless connection or, alternatively or additionally, a usercan provide information between the electrical stimulation system 512and the computer 500 using a computer-readable medium or by some othermechanism. In some embodiments, the computer 500 may include part of theelectrical stimulation system.

In at least some instances, a treating physician may wish to tailor thestimulation parameters (such as which one or more of the stimulatingelectrode contacts to use, the stimulation pulse amplitude (such ascurrent or voltage amplitude depending on the stimulator being used,)the stimulation pulse width, the stimulation frequency, or the like orany combination thereof) for a particular patient to improve theeffectiveness of the therapy. Electrical stimulation systems can providean interface that facilitates parameter selections. Examples of suchsystems and interfaces can be found in, for example, U.S. Pat. Nos.8,326,433; 8,831,731; 8,849,632; 9,050,470; and 9,072,905; and U.S.Patent Application Publication No. 2014/0277284, all of which areincorporated herein by reference in their entireties.

Stimulation region visualization systems and methods can be used topredict or estimate a region of stimulation for a given set ofstimulation parameters. In at least some embodiments, the systems andmethods further permit a user to modify stimulation parameters andvisually observe how such modifications can change the predicted orestimated stimulation region. Such algorithms and systems may providegreater ease of use and flexibility and may enable or enhance specifictargeting of stimulation therapy. The term “volume of activation” (VOA)will be used to designate an estimated region of tissue that will bestimulated for a particular set of stimulation parameters.

The terms “stimulation field map” (SFM) and “volume of tissueactivation” (VTA) also refer to the VOA. Examples of methods fordetermining the VOA can be found in, for example, U.S. Pat. Nos.7,346,282; 8,180,601; 8,209,027; 8,326,433; 8,589,316; 8,594,800;8,606,360; 8,675,945; 8,831,731; 8,849,632; 8.958,615; 9.020,789; andU.S. Patent Application Publications Nos. 2009/0287272; 2009/0287273;2012/0314924; 2013/0116744; 2014/0122379; 2015/0066111; and2016/0030749, all of which are incorporated herein by reference.

In at least some methods of estimating or determining a VOA, theelectric field arising from the electrical energy delivered according tothe stimulation parameters is determined or modeled, the tissue responseto an electrical field is also determined or modeled, and then the VOAcan be identified or estimated. There are a variety of methods fordetermining or modeling an electric field including, but not limited to,a finite element analysis model described in, for example, thereferences cited in the preceding paragraph, although it will berecognized that other models (including other models described in thereferences cited in the preceding paragraph) can also be used. There arealso a variety of method for determining or modeling tissue including,but not limited to, a neural element model or axon model as describedin, for example, the references cited in the preceding paragraph,although it will be recognized that other models (including other modelsdescribed in the references cited in the preceding paragraph) can alsobe used.

In at least some embodiments, the information based on the electricfield model and tissue response model can be used to produce planardistributions of stimulation threshold values for a series of planes 450distributed around a lead 400 having electrodes 425, as illustrated inFIG. 4A. In at least some embodiments, these stimulation thresholdvalues may be dependent on other stimulation parameters, such asstimulation duration (for example, pulse width), stimulation frequency,and the like.

Each of the planes 450 can be divided into multiple regions (forexample, squares or rectangles) with an associated stimulation thresholdvalue (such as a threshold current or voltage) which, when applied tothe lead will activate or stimulate the tissue at that region, asillustrated in FIG. 4B. For discussion purposes, the stimulationthreshold value will be considered a threshold current, I_(th) , but itwill be recognized that a threshold voltage or other electricalcharacteristic may be used instead. Each region of each plane 450 can becharacterized by an x-value, which corresponds to a radial distance fromthe lead 400, a z-value, which corresponds to an axial coordinate alongthe longitudinal axis of the lead, and a θ-value, which corresponds tothe relative angle of the plane in which the region resides. Thesecoordinates are labeled in FIGS. 4A and 4B. Thus, the values of I_(th)can be stored in a database as a series of I_(th) tables, I_(th)(z, x,θ), which can also be indexed relative to other state variables, asdescribed below. A visual example of these I_(th) tables 450 a, 450 b,450 n is presented in FIG. 4B where each plane 450 of FIG. 4A representsone of the tables 450 a, 450 b, . . . 450 n wherein the number in eachcell of the table represents the current at which a neural fiber locatedat the center of the cell would be activated. Although the exampleillustrated in FIG. 4B has four z values, 3 x values, and one table forevery 60 degrees of θ, it will be recognized that the number of valuesfor z and x and the θ separation for each table can be any number. Thetables of FIG. 4B are merely provided for illustrative purposes.

The I_(th) values may also depend on other stimulation parameters, suchas pulse width (“pw”), pulse frequency (“freq”), and the distribution ofthe electrical energy (or current or voltage) between the differentelectrodes (which can be referred to as “fractionalization”). Thus, whenthese factors are considered, the database is expanded to I_(th)(z, x,θ, pw, freq, fractionalization). Other stimulation parameters may beadded to this set. The database may also be visualized as a set oftables 450 a, 450 b, . . . 450 n (as illustrated in FIG. 4B) for eachunique selection of the pulse width, frequency, and fractionalizationparameters.

Fractionalization is the distribution of the electrical energy (orcurrent or voltage) between the electrodes of the lead and can beexpressed, for example, by an additional set of parameters: axialposition, rotation, and spread. For purposes of illustration of thesethree parameters, one embodiment of a distal end of a lead 500 ispresented in FIG. 6. The lead 500 includes a ring electrode 550, a firstset of three segmented electrodes 552 a, 552 b, 552 c, a second set ofthree segmented electrodes 554 a, 554 b, 554 c, and a tip electrode 556.An “axial position” variable can be used to estimate or represent thecentral axial position of the field relative to the longitudinal axis ofthe lead. For example, if the stimulation is provided solely by ringelectrode 550, then the axial position of the field is centered on theaxial position of the ring electrode 550. However, combinations ofelectrodes can also be used. For example, if the stimulation is providedwith 50% of the current amplitude on ring electrode 550 and 50% of thecurrent amplitude on segmented electrode 552 a, then the axial positionof the field can be described as centered axially between electrode 550and electrode 552 a (although it will be recognized that the field alsoextends in both axial directions from this axial position.) If thestimulation is provided with 75% of the current amplitude on ringelectrode 550 and 25% of the current amplitude on segmented electrode552 a, then the axial position of the field can be described as centeredaxially between electrode 550 and electrode 552 a, but closer to ringelectrode 550. In at least some embodiments, a specific number ofdifferent axial position values can be defined for the system.

For example, in one embodiment, 31 different axial position values canbe defined for the lead illustrated in FIG. 6. Four of the axialpositions correspond to 1) electrode 550, 2) electrodes 552 a, 552 b,552 c, 3) electrodes 554 a, 554 b, 554 c, and 4) electrode 556. Inaddition, nine axial positions can be defined between adjacent pairs ofthese four axial positions (e.g., 1) 90% of current amplitude onelectrode 550 and 10% of current amplitude on electrodes 552 a, 552 b,552 c, 2) 80% on electrode 550 and 20% on electrodes 552 a, 552 b, 552c, . . . 8) 20% on electrode 550 and 80% on electrodes 552 a, 552 b, 552c, and 9) 10% on electrode 550 and 90% on electrodes 552 a, 552 b, 552c).

Another parameter is “rotation” which represents the angular directionof the field extending away from the lead. In the case of stimulationprovided solely by ring electrode 550, the rotation parameter isarbitrary because the stimulation is provided equally in all directions.On the other hand, if the stimulation is provided by segmented electrode552 a, the rotation can be described as directed outward from segmentedelectrode 552 a. Again, combinations of electrodes can be used so thatthe rotation may be described as centered between electrodes 552 a, 552b if 50% of the stimulation amplitude is provided to both electrodes. Inat least some embodiments, a specific number of different rotationvalues can be defined for the system.

For example, in one embodiment, 12 different rotation values are definedfor the lead illustrated in FIG. 6. For example, three of the rotationvalues correspond to the angular positions of 1) electrodes 552 a, 554a, 2) electrodes 552 b, 554 b, and 3) electrodes 552 c, 554 c. Inaddition, three additional rotation values can be defined betweenadjacent pairs of these three rotation values (e.g., 1) 75% on electrode552 a and 25% on electrode 552 b, 2) 50% on electrode 552 a and 50% onelectrode 552 b; and 3) 25% on electrode 552 a and 75% on electrode 552b).

Yet another parameter is “spread” which relates to the angular spread ofthe field around the circumference of the lead. In the case ofstimulation provided solely by ring electrode 550, the spread variableis at a maximum because the stimulation is provided equally in alldirections. On the other hand, if the stimulation is provided bysegmented electrode 552 a, the spread variable is at its minimum becausethe field is generated using only one segmented electrode 552 a. Again,combinations of electrodes can be used. For example, the spread may bedescribed as intermediate between the two previous examples when 50% ofthe stimulation amplitude is provided on both electrodes 552 a, 552 b.In at least some embodiments, a specific number of different spreadvalues can be defined for the system.

For example, in one embodiment, 11 different spread values are definedfor the lead illustrated in FIG. 6. For example, one spread valuecorresponds an equal field in all directions (such as, the fieldgenerated by electrode 550 or electrode 556) and another spread valuecorresponds to a field generated by one of the segmented electrodes(e.g., electrode 552 a). The other nine spread values are between thesetwo extremes.

The stimulation (e.g., stimulation current) can be steered to differentpositions and arrangements around the lead which results in changes inthese fractionalization parameters: axial position, rotation, andspread. For example, the stimulation can be moved up or down thelongitudinal axis of the lead thereby changing the axial positionparameter. As an example, the stimulation can be initially provided 100%through electrode 550. The stimulation can then be steered distally bydirecting a portion of the stimulation to the electrodes 552 a, 552 b,552 c. For example, in a first step, 90% of the stimulation remains onelectrode 550 and 10% is divided equally among electrodes 552 a, 552 b,552 c. The second step can have 80% on electrodes 550 and 20% dividedequally among electrodes 552 a, 552 b, 552 c. This can continue untilthere is no stimulation on electrode 550 and 100% of the stimulation isdivided among electrodes 552 a, 552 b, 552 c. The process can proceed toincrementally transfer stimulation from electrodes 552 a, 552 b, 552 cto electrodes 554 a, 554 b, 554 c. Similarly, the stimulation then beincrementally transferred from electrodes 554 a, 554 b, 554 c toelectrode 556.

The stimulation can also be rotated. For example, stimulation fromelectrode 552 a can be rotated to electrode 552 b in stepped increments.The stimulation field can also be spread. For example, stimulation fieldfrom electrode 552 a can be spread so that the stimulation arises fromboth electrodes 552 a, 552 b. That stimulation field can then becontracted so that the stimulation is only from electrode 552 b.

It will be recognized that the resulting I_(th) database can be quitelarge depending on the number of different values for each of theparameters. As one example, such an I_(th) database can be generated fora set of fractionalization states obtained using 11 different spreadvalues, 12 different rotation values, and 31 different axial positionvalues, as well as multiple values of the other variables (for example,43 values for z, 16 values for r, 12 values for θ, 12 values for pulsewidth, and 45 values for frequency).

The database can be compressed using one or more techniques. As oneexample, the database can be compressed (for example, the amount ofstored data decreased) when it is recognized that many fractionalizationstates are not unique or are not available. The amount of data storedcan be reduced by taking advantage of the unavailability offractionalization states, as well as redundancy and symmetry in thefractionalization states. In at least some embodiments, the database canbe reduced to a set of unique I_(th) tables (such as those illustratedin FIG. 4B) and a map M which relates the I_(th) tables to the differentfractionalizations (i.e., the different axial position, rotation, andspread values) and, optionally, to different pulse widths orfrequencies.

Using lead 500 of FIG. 6 as an example with 11 different spread values,12 different rotation values, and 31 different axial position values, asdescribed above, there are potentially 4092 different fractionalizationstates. However, a number of these states are not actually available orare redundant. For example, any stimulation that utilizes only ringelectrode 550 for delivery of the stimulation will have the maximumspread value (because the other spread states, with a smaller degree ofspread, cannot be produced using only the ring electrode 550) androtation value will be irrelevant because there is no identifiableangular direction of the stimulation because stimulation by the ringelectrode 550 is cylindrically symmetric. Although there are potentially121 different possible combinations of spread and rotation for eachaxial position value, when the axial position value corresponds tostimulation using the ring electrode only, there is only 1 non-redundantfractionalization state. Thus, the number of actual availablefractionalization states associated with stimulation using only one ofthe ring electrodes is reduced by 120.

As another example, when the stimulation is divided equally among 552 a,552 b, 552 c (i.e., the spread variable value is maximum), then therotation value is again irrelevant because there is no identifiableangular direction for the stimulation and therefore, although there are12 potential selections of rotation, there is actually only 1 availablerotation state. Thus, the number of actual available states associatedwith stimulation using maximum spread over all of the segmentedelectrodes of one set is reduced by 12.

Using similar observations, it is found that, for 31 axial positionvalues, 12 rotation values, and 11 spread values and assumingsymmetrical tissue response, the 4092 total states can be reduced to 828unique fractionalization states that can be selected for the electrodesof the lead in FIG. 6.

In addition to reducing the number of unique or possiblefractionalization states, symmetry can be used to compress the storeddata. Assuming that the tissue response is the same in all directions,then the I_(th) values for stimulation using only electrode 552 a(fractionalization state 1) will be the same as the I_(th) values forstimulation using only electrode 552 b (fractionalization state 2)except for a 120 degree rotation and will be the same as the I_(th)values for stimulation using electrode 552 c (fractionalization state 3)except for a −120 degree rotation. In other words, I_(th,1)(x, z,θ)=I_(th,2)(x, z, θ−120) =I_(th,3)(x, z, θ+120) where I_(th,1)=thethreshold table for fractionalization state 1,I_(th,2)=the thresholdtable for fractionalization state 2, and I_(th,3)=the threshold tablefor fractionalization state 3. Because of this symmetry, only one set ofI_(th) tables is stored for these three fractionalization states becausethe same set of I_(th) tables by mapping the I_(th) tables accountingfor the rotation described above. Thus, the number of I_(th) tablesneeded in the database is less due to the recognition of the symmetry.This equivalence of the I_(th) tables, except for a rotation, forsimilar states is available for many fractionalizations. For example, afractionalization that includes stimulation provided by a combination ofelectrode 556 and electrode 554 a (with a particular apportioning of thestimulation between the two electrodes, for example, 70%/30%) is similarto stimulation provided by a combination of electrode 556 and electrode554 b (with the same apportioning of the stimulation between the twoelectrodes) except for a rotation of 120 degrees. In this example, thesame set of I_(th) tables can be used with the mapping taking intoaccount the rotation. As another example, stimulation provided by acombination of electrodes 554 a and 554 b (with a particularapportioning of the stimulation between the two electrodes, for example,70%/30%) is similar to a combination of electrodes 554 b and 554 c (withthe same apportioning of the stimulation between the two electrodes)except for a rotation of 120 degrees. Again, in this example, the sameset of I_(th) tables can be used with the mapping taking into accountthe rotation.

Similarly, in many instances the stimulation field will have mirrorsymmetry about the central radial axis of the stimulation field. Inother words, I_(th)(x, z, θ)=I_(th)(x, z, −θ) and, therefore, in theseinstances, only I_(th)(x, z, θ) for values of θ from 0 to 180 degreesneeds to be stored in the database because I_(th)(x, z, θ) for values ofθ between 180 and 360 degrees, non-inclusive of the endpoints,corresponds to one of the stored I_(th)(x, z, θ). Again, a map can beused to map the stored I_(th) tables to the large set of I_(th)(x, z, θ,fractionalization), but the number of I_(th) tables that are need to bestored in the database is less due to the recognition of the symmetry.

It will be recognized that other symmetries can be identified and thatthere may also be symmetries that are applicable based on pulse width orfrequency stimulation parameters. Therefore, as illustrated in FIG. 7, aset of unique I_(th,unique) tables 760 (such as I_(th,unique)(x, z, θ))form a compressed database and are identified, as well as a map 762 thatrelates the I_(th,unique) tables to the full set of I_(th,full) tables764 (such as I_(th,full)(x, z, θ, fractionalization) or I_(th,full)(x,z, θ, fractionalization, pw, frequency)). This arrangement is a losslesscompression of the I_(th) data because the full set of I_(th) data canbe reconstructed from the I_(th,unique) tables and map.

Alternatively or additionally, lossy compression may also be applied tothe I_(th,unique) tables or full I_(th) data. As illustrated in FIG. 8,a set of unique, approximate I_(th,approx) tables 861 form a compresseddatabase and are identified with a map 862 that relates theI_(th,approx.) tables to the I_(th,full) tables 860. This is a lossycompression because the I_(th,approx.) tables 861 are not necessarilythe same as the I_(th,full) tables that they represent, but rather theI_(th,approx.) tables are sufficiently similar (based on a similaritymetric) to the original I_(th,full) tables that they represent to beacceptable to the user.

In some embodiments of lossy compression, a group of similar I_(th)tables are approximated using a single I_(th,approx) table. As anexample, a similarity metric may be used to compare a particular I_(th)table with a particular I_(th,approx) table and, when the similaritymetric is within a specified tolerance, the original I_(th) table can berepresented by the I_(th,approx) table in the compressed I_(th)database. In this manner, the large set of I_(th) tables can berepresented by fewer I_(th,approx) tables. Any suitable similaritymetric can be used including, but not limited to, the sum of the of thesquared differences between corresponding entries in the I_(th) tableand the I_(th,approx) table. Moreover, any suitable number ofI_(th,approx) tables can be selected including 10, 50, 100, 200, 300,400, 500 or more tables.

Another lossy compression method utilizes MPEG compression or a processsimilar to MPEG compression. MPEG video compression is a procedure thatlooks at the differences from frame to frame in a video sequence and,instead of generating data describing each frame, generates datadescribing differences from the previous frame.

In one example of a lossy compression method for I_(th) data, asimilarity metric is selected such as the sum of the of the squareddifferences between corresponding entries in a particular I_(th) tableand a selected base I_(th) table. A sequence of I_(th) tables can thenbe built from this base I_(th) table. In some embodiments, an orderedlist is created starting with the I_(th) tables most similar to the baseI_(th) table and continuing to less similar I_(th) tables. This cangenerate a linear succession of I_(th) tables. In other embodiments, abranched sequence of I_(th) tables can be created by building aconnected non-looping sequence linking all I_(th) tables to their leastdifferent counterparts. From the base I_(th) table, there can bemultiple branches with each branch being generated based on similarityof the I_(th) tables along that branch.

In some embodiments, all of the I_(th) tables will be located in alinear or branched sequence using a single base I_(th) table. In otherembodiments, two or more base I_(th) tables are selected (preferably,based on substantial differences between the base I_(th) tables) and theremainder of the I_(th) tables are associated with one of the baseI_(th) tables (for example, the most similar of the base I_(th) tables)and linear or branched sequences of I_(th) tables are generated usingeach of the base I_(th) tables.

Once a linear or branched sequence of I_(th) tables is generated, theindividual I_(th) tables in the sequence can be considered image framesand compressed into a compressed database using a MPEG compressionalgorithm that, instead of storing the individual I_(th) tables in thecompressed database, stores the base I_(th) table(s) and then proceedsalong each linear or branched sequence storing the difference betweenthe current table and the preceding table. Again, a map is used toidentify which data also the sequence corresponds to a particular I_(th)table. When a particular I_(th) table is subsequently needed, thecompressed database and map are used to retrieve the I_(th) table fromthe stored data.

The lossless or lossy compressed databases described above can be storedin any suitable memory and then used to generate a volume of activation.FIG. 9 illustrates one method of estimating a volume of activation. Instep 980, the system receives or is otherwise provided with a set ofstimulation parameters with include a stimulation amplitude and aselection of one or more electrodes (referred to above as the“fractionalization”) for delivery of the stimulation and may alsoinclude other parameters such as pulse width, frequency, or the like. Instep 982, the system determines an estimate of the volume of activationusing the set of stimulation parameters, the compressed database (suchas database 760 or database 861), and the map (such as map 762 or map862). For example, the set of stimulation parameters, compresseddatabase, and map are used to obtain I_(th) data corresponding to theset of stimulation parameters. For example, the I_(th,unique) orI_(th,approx.) tables of the compressed database can be identified forthe designated fractionalization, pulse width, and frequency. Theidentified I_(th, unique) or I_(th,approx.) tables provided a spatialdistribution in z, x, and θ of the threshold values for stimulation ofneural elements. Using the stimulation amplitude and these thresholdvalues, the system can estimate which regions will have neural elementsthat are stimulated for the given set of stimulation parameters.

In step 984, this estimated region can then be displayed graphically forthe user. In optional step 986, the user may direct the system to outputthe stimulation parameters to a stimulation device, for example, thecontrol module 514 of FIG. 5, that can produce stimulation signals fordelivery to the patient via the lead electrodes. The stimulation devicecan receive the stimulation parameters and can then operate astimulation program to deliver electrical stimulation to the patientusing the stimulation parameters.

FIG. 10 illustrates one method of producing a compressed database. Instep 1092, the system receives or produces planar distributions ofstimulation threshold values for multiple sets of stimulationparameters. In step 1094, this data is compressed using one or more ofthe lossless or lossy compression methods described above to produce thecompressed database.

A compressed database can be fully or partially decompressed. FIG. 11illustrates one method of decompressing a compressed database. In step1196, the compressed database and map is provided. In step 1198, the mapis used to fully or partially compress the compressed database. For alossless compressed database, this decompression regenerates theoriginal database or a part of the original database. For a lossycompressed database, the decompression creates a new full or partialuncompressed database that utilizes only I_(th,approx.) tables and,therefore, is an approximation of the original database. In someembodiments, only part of the compressed database is uncompressed. Thispart may be selected based on selections of certain stimulationparameter values. For example, the portion of the compressed databasefor a particular selection of electrodes or a particular selection ofpulse width or frequency (or ranges of these values) may bedecompressed. In some embodiments, this decompression may occur as partof a procedure for estimating a volume of activation (similar to step982 of FIG. 9 except that a portion of the database is decompressed inthis step). In some embodiments, decompression of different portions ofthe database may be performed sequentially during any suitableprocedure. In some embodiments, the database may be compressed forstorage or transfer to another device and then decompressed upontransfer to the other device or retrieval from storage.

The methods and systems described herein may be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. Accordingly, the methods and systemsdescribed herein may take the form of an entirely hardware embodiment,an entirely software embodiment or an embodiment combining software andhardware aspects. Systems referenced herein typically include memory andtypically include methods for communication with other devices includingmobile devices. Methods of communication can include both wired andwireless (e.g., RF, optical, or infrared) communications methods andsuch methods provide another type of computer readable media; namelycommunication media. Wired communication can include communication overa twisted pair, coaxial cable, fiber optics, wave guides, or the like,or any combination thereof. Wireless communication can include RF,infrared, acoustic, near field communication, Bluetooth™, or the like,or any combination thereof.

It will be understood that each block of the flowchart illustrations,and combinations of blocks in the flowchart illustrations and methodsdisclosed herein, can be implemented by computer program instructions.These program instructions may be provided to a processor to produce amachine, such that the instructions, which execute on the processor,create means for implementing the actions specified in the flowchartblock or blocks disclosed herein. The computer program instructions maybe executed by a processor to cause a series of operational steps to beperformed by the processor to produce a computer implemented process.The computer program instructions may also cause at least some of theoperational steps to be performed in parallel. Moreover, some of thesteps may also be performed across more than one processor, such asmight arise in a multi-processor computer system. In addition, one ormore processes may also be performed concurrently with other processes,or even in a different sequence than illustrated without departing fromthe scope or spirit of the invention.

The computer program instructions can be stored on any suitablecomputer-readable medium including, but not limited to, RAM, ROM,EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (“DVD”) or other optical storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other medium which can be used to store the desired informationand which can be accessed by a computer.

The above specification and examples provide a description of theinvention and use of the invention. Since many embodiments of theinvention can be made without departing from the spirit and scope of theinvention, the invention also resides in the claims hereinafterappended.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. A system for estimating a volume of activationaround an implanted electrical stimulation lead for a set of stimulationparameters, the system comprising: a display; and a processor coupled tothe display and configured to: receive a set of stimulation parameterscomprising a stimulation amplitude and a selection of one of moreelectrodes of the implanted electrical stimulation lead for delivery ofthe stimulation amplitude; determine an estimate of the volume ofactivation based on the set of stimulation parameters using thestimulation amplitude and a database comprising a plurality of planardistributions of stimulation threshold values and a map relating theplanar distributions to spatial locations based on the one or moreelectrodes of the implanted electrical stimulation lead selected fordelivery of the stimulation amplitude; and output on the display agraphical representation of the estimate of the volume of activation. 2.The system of claim 1, wherein the database consists of the plurality ofplanar distributions, wherein each of the planar distributions isunique.
 3. The system of claim 2, wherein the map comprises a pluralityof entries, wherein each entry is indexed to a selection of the one ormore electrodes and an angular location around the implanted electricalstimulation lead.
 4. The system of claim 3, wherein the selection of theone or more electrodes is characterized by at least onefractionalization parameter.
 5. The system of claim 4, wherein the atleast one fractionalization parameter comprises at least one of an axialposition parameter, an angular direction parameter, or an angular spreadparameter.
 6. The system of claim 3, wherein the selection of the one ormore electrodes is characterized by an axial position parameter, anangular direction parameter, and an angular spread parameter.
 7. Thesystem of claim 3, wherein at least two of the entries of the map pointto a same planar distribution.
 8. The system of claim 7, wherein the atleast two of the entries comprise a first entry indexed to a selectionof a first one of the electrodes and a first angular location and asecond entry indexed to a selection of a second one of the electrodesand a second angular location, wherein the first angular location andthe second angular location differ by a first angle, wherein a locationof the first one of the electrodes differs from a location of the secondone of the electrodes by the first angle.
 9. The system of claim 2,wherein the database is a lossless compressed database.
 10. The systemof claim 2, wherein the database is a lossy compressed database.
 11. Anon-transitory computer-readable medium having computer executableinstructions stored thereon that, when executed by at least oneprocessor, cause the at least one processor to perform the instructions,the instructions comprising: receiving a set of stimulation parameterscomprising a stimulation amplitude and a selection of one of moreelectrodes of the implanted electrical stimulation lead for delivery ofthe stimulation amplitude; determining an estimate of the volume ofactivation based on the set of stimulation parameters using thestimulation amplitude and a database comprising a plurality of planardistributions of stimulation threshold values and a map relating theplanar distributions to spatial locations based on the one or moreelectrodes of the implanted electrical stimulation lead selected fordelivery of the stimulation amplitude; and outputting, on the display, agraphical representation of the estimate of the volume of activation.12. The non-transitory computer-readable medium of claim 11, wherein thedatabase consists of the plurality of planar distributions, wherein eachof the planar distributions is unique.
 13. The non-transitorycomputer-readable medium of claim 12, wherein the map comprises aplurality of entries, wherein each entry is indexed to a particularselection of the one or more electrodes and a particular angularlocation around the implanted electrical stimulation lead.
 14. Thenon-transitory computer-readable medium of claim 13, wherein theselection of the one or more electrodes is characterized by at least onefractionalization parameter.
 15. The non-transitory computer-readablemedium of claim 13, wherein at least two of the entries of the map pointto a same planar distribution.
 16. The non-transitory computer-readablemedium of claim 12, wherein the database is a lossless compresseddatabase.
 17. The non-transitory computer-readable medium of claim 12,wherein the database is a lossy compressed database.
 18. A system forestimating a volume of activation around an implanted electricalstimulation lead for a set of stimulation parameters, the systemcomprising: a processor configured to: receive a plurality of planardistributions of stimulation threshold values for each of a plurality ofsets of stimulation parameters, wherein each of the sets of stimulationparameters comprises a stimulation amplitude and a selection of one ofmore electrodes of the implanted electrical stimulation lead fordelivery of the stimulation amplitude; compress the plurality of planardistributions of stimulation threshold values into a compressed databasecomprising a plurality of unique planar distributions of stimulationthreshold values; and generate a map relating the unique planardistributions of stimulation threshold values to the planardistributions of stimulation threshold values for the multiple sets ofstimulation parameters.
 19. The system of claim 18, wherein thecompressing comprises compress the plurality of planar distributions ofstimulation threshold values into a compressed database using a losslesscompression technique.
 20. The system of claim 18, wherein thecompressing comprises compress the plurality of planar distributions ofstimulation threshold values into a compressed database using a lossycompression technique.